What type of Engine Oil do y'all use? I had heard at a seminar that m/c's need m/c oil and that normal automotive oil when new is only as good as used m/c oil. My Guzzi mechanic says he uses 20W50 Motor Oil (Quaker state or Pennsoil - PA oils). I have heard Mobil 1 is a good choice but can cause leaks. Any input?